Unsafe conditions may occur when an onboard flight control system or similar critical control system is impacted by a cyberintrusion. This impact may be reduced, and unsafe conditions prevented, by detecting the intrusion and performing appropriate countermeasures. For example, a cyberintrusion may be detected by independent dissimilar monitoring of critical control systems. A simplified model of the control system may be created and implemented into an intrusion detection system. Alternatively, the control system may be independently implemented to create a dissimilar, but equivalent, monitoring system. However, both of these approaches may significantly drain available resources.